This invention relates to a novel one-stage process for the production of polyoxyalkylene containing polyols which have equivalent weights of about 150 to about 6000 and functionalities of about 2 to 8.
Polyoxyalkylene containing monols and polyols are typically prepared by the reaction of a suitable starter (or initiator) compound with one or more alkylene oxides in the presence of one or more catalysts. In general, suitable starters or initiators include compounds having at least one hydroxyl group per molecule (i.e. alcohols) and preferably having two or more hydroxyl groups per molecule (i.e. diols, triols, and other higher polyols). Polyoxyalkylene containing polyols of this type are well known in the field of polyurethane chemistry.
Various references including, for example, U.S. Pat. Nos. 6,136,879 and 6,204,300 and EP 1457508 A1 describe the production of polyurethane foams from different polyol components. The foams of these references are low resilience flexible polyurethane foams. Both U.S. Pat. No. 6,136,879 and EP 1457508 disclose that suitable starters for the polyol components therein include compounds such as bisphenol A. However, neither reference actually prepares or uses such a polyol.
In addition, U.S. Pat. No. 6,136,879 discloses the preparation of polyurethane foams having a low rebound resilience and a low temperature dependence on the compression force deflection. These foams comprise the reaction product of a polyisocyanate with a polyol component and water, in the presence of a small quantity of an alkyl phenol. These alkyl phenols may be alkoxylated with ethylene oxide and/or propylene oxide.
Phenols are aromatic organic compounds that have one or more hydroxyl groups attached directly to the benzene ring. Although phenols contain hydroxyl groups like alcohols, their properties are clearly different than alcohols in which the hydroxyl groups are attached directly to an aliphatic or cycloaliphatic carbon atom. It is known in the art to alkoxylate diphenols and phenolic resins to prepare polyether polyols, however the preparation of these phenolic based polyols is more problematic than the preparation of polyols from starters bearing aliphatic hydroxyl groups. As described in U.S. Pat. No. 6,541,673, the decreased basicity of the alkali metal phenoxides (compared to alkali metal alkoxides) lowers the oxyalkylation rate considerably, and the reaction generally proceeds with a long induction time prior to attaining a reasonable oxyalkylation rate. It is also known that the alkylene oxides are poorly soluble in phenolic compounds, and thus a solvent (preferably toluene or xylene) is required for the oxyalkylation of phenolic starters. The addition of solvent, however, slows the oxyalkylation rate and also requires an additional processing step to remove it from the product. Another problem in preparing phenolic initiated polyols is that an increase in the reaction temperature to increase the oxyalkylation rate broadens the molecular weight distribution and increases the color of the product.
U.S. Pat. No. 4,846,996 describes liquid non-crystallizing two mole diphenol alkoxylate mixtures. These are prepared by the reaction of a mixture of two different alkylene oxides with a diphenol in the presence of an alkaline catalyst. These diphenol mixtures correspond to a specific formula, and are liquids at room temperature and may not crystallize even when stored for long time periods at sub-ambient temperatures. Mixtures of the diphenols of the specified formula comprise three components in relative amounts as specified. Outside of these ranges of the three components, the mixtures are solids and tend to crystallize.
Phenolic polymers prepared by aralkylation reactions are disclosed in U.S. Pat. No. 5,889,137. These phenol aralkylation polymers are derived from a phenolic monomer, at least one styrene derivative and an aryl diolefin. More specifically, these are prepared by aralkylating a phenolic monomer with at least one styrene derivative to form an aralkylated phenol, then reacting the aralkylated phenol with an aryl diolefin to produce the phenol aralkylation polymer, in which the aralkylated phenol is coupled via the aryl diolefin. When the primary linkage is in the ortho position, the resultant polymer has a lower melting point, and when the primary linkage is in the para position, the resultant polymer has a higher melting point.
Phenolic resin polyols based on aralkylated phenolics are described in U.S. Pat. Nos. 6,127,491 and 6,569,953. These polyols are the reaction product of an aralkylated phenol or phenol aralkylation polymer with an oxyalkylating agent which may be an alkylene oxide or an alkylene carbonate. The aralkylated phenols useful are those derived from a phenolic monomer, at least one styrene derivative and a coupling agent such as, for example, an aryl diolefin.
In U.S. Pat. No. 6,541,673, a process to overcome many of the aforementioned problems with oxyalkylating phenolic compounds to produce polyether polyols is described. It discloses that significant improvements are made in the preparation of aryl polyols by a staged temperature process in which a first oxyalkylation is conducted at a relatively high temperature, and further oxyalkylation is conducted at a lower temperature. This yields products in which the viscosity and polydispersity remain substantially the same, and in some cases lower compared with the lower temperature or solvent based processes. Also, the lower temperature and/or solvent based processes suffer from longer induction periods and overall reaction times, compared to the process of U.S. Pat. No. 6,541,673. Suitable aryl polyols include those produced by oxyalkylating a phenolic starter molecule containing at least two phenolic hydroxyl groups, and up to 10 or more hydroxyl groups. The starters for the polyols of this invention may be single or condensed rings. Preferred starters have non-condensed aryl groups linked to phenolic hydroxyl-containing rings through alkylene linking groups. This process requires the oxyalkylation be performed at two different temperatures, with the first being significantly higher than 135° C., (normal oxyalkylation temperature 100-125° C.), and preferably higher than 140° C. This high temperature oxyalkylation occurs first, and preferably at least 20% of the total oxyalkylation occurs at the high temperature. Then, the low temperature oxyalkylation follows, and preferably at least 20% of the total oxyalkylation is carried out at the low temperature. Although a process using the heel of a prior batch is discussed in Example 6 and Comparative Example 7, these are two-stage processes. U.S. Pat. No. 6,541,673 discloses that the viscosity of the resultant product increases when the two stage oxyalkylation process is not used.
Finally, U.S. Pat. No. 6,624,333 discloses a method for producing bisphenol alkoxylates. This process comprises reacting at least one bisphenol with alkylene oxide in the presence of a phosphine catalyst, which is essentially free of alkali metal hydroxide. Bisphenol A (i.e. BPA) is disclosed as a suitable bisphenol compound for this process. In a preferred embodiment, the bisphenol dialkoxylates are converted into the higher alkoxylated bisphenol alkoxylates in a subsequent reaction with an alkylene oxide.
Several commercially important bisphenol derivatives that would be useful as starters for polyether polyols are very high melting solids that would require either solvent or reaction temperatures in excess of the m.p. of the starter (i.e. >160° C.) to alkoxylate. These include bisphenol A, i.e. 2,2-bis(4-hydroxyphenyl)propane, (m.p. 158-160° C.); 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, i.e. bisphenol TMC, (m.p. 204-206° C.); and 4,4′-(1-methylethylidene)bis[2,6-dibromophenol] (Tetrabromobisphenol A) (m.p. 179-182° C.). Surprisingly, it has been found that polyether polyols based on these and other phenolic or polyphenolic starters can be prepared in a single stage heel process at temperatures significantly below the melting point of the starter, in the absence of solvent. Since the process relies upon dispersing or dissolving the starter in a carrier (the heel) of a liquid hydroxyl or polyhydroxyl containing component, difficulties with melting and stirring solid starters are avoided. The processing temperatures are below those required by the two-stage process of U.S. Pat. No. 6,541,673. Also, since the process does not require a first alkoxylation at a higher temperature followed by a decrease in the temperature during the run, it is less energy intensive.